Unless otherwise indicated herein, the approaches described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
Increasing demand for wireless data traffic has created opportunities for new network architectures incorporating multitier base stations (BSs) with various sizes and capabilities. Some cellular communication systems employ small-sized low-power BSs, such as femtocell BSs, because of their advantages such as low cost deployments, traffic offloading from macrocells, etc. Femtocell BSs may be BSs with the size comparable to customer-premises equipment (CPE) or Wi-Fi access point (AP), which typically may provide indoor wireless coverage to mobile stations (MSs) using fixed broadband Internet connections.
Mass deployment of femtocells in existing mobile communication networks may create various technical challenges, such as interference between neighboring femtocells as well as between femtocells and macrocells, because femtocells may share the same licensed frequency spectrum with macrocells. In order to reduce the interference between femtocells and macrocells as well as power consumption in femtocells, an optional operation mode such as a low duty mode (LDM) in IEEE 802.16m (WiMAX-Advanced) and a dormant mode in Global System for Mobile Communications (GSM) or in Long Term Evolution (LTE) may be used. In these operation modes, air interface activity may be reduced as much as possible if there are no mobile stations connected to femtocell BSs or opportunistic small cells.
In order to detect the proximity of mobile stations at a small cell, the small cell should continue to monitor cellular uplink signals even in the LDM or dormant mode. However, such always-on cellular uplink signal monitoring may be a burden in terms of uplink decoding time and power consumption. Furthermore, the detection of proximity by monitoring for the cellular uplink signal to macrocell BSs or femtocell BSs may not be accurate due to an imbalance of uplink coverage between femtocell and macrocell BSs.